Glyphosate, N-(phosphonomethyl)glycine, is a well-known widely used herbicide. It is generally employed in the form of an agriculturally acceptable salt.
In U.S. Pat. No. 5,116,401 to D. C. Young it is pointed out that although glyphosate is a very active, broad spectrum, systemic, relatively environmentally safe herbicide, its solubility in water at 25.degree. C. is only 1.2 weight percent and many of its homologs and salts are only slightly soluble or are essentially insoluble in water and organic solvents. Thus in practice, formulations of glyphosate salts with other components to enhance its solubility and its effectiveness are typically used.
Over the years a wide variety of substances, including surfactants, have been studied or proposed as adjuvants to enhance the effectiveness of glyphosate. For example, J. W. Kassebaum and H. C. Berk indicate in U.S. Pat. No. 5,317,003, that surfactants are usually employed to enhance the effectiveness of glyphosate when it is applied to the foliage of various plants, and that the most widely used surfactant in commercial compositions is an ethoxylated fatty amine. In addition, they refer to knowledge in the art that a particular surfactant used in an aqueous composition with a herbicide can enhance the effectiveness of the herbicide, whereas other surfactants have very little, if any, beneficial effect. They also note that some surfactants may exhibit antagonistic effects. As an example they cite the work of Wyrill and Burnside, Weed Science, Volume 25, (1977), pages 275-287 wherein, among other things, it was found that the surfactant ETHOQUAD 18/12 was relatively ineffective in enhancing phytotoxicity of glyphosate to hemp dogbane whereas in a separate experiment an analogous compound, ETHOQUAD 18/25, was one of the most effective surfactants tested.
Despite the extensive studies and efforts devoted to improving the performance of glyphosate, a need exists for a way of potentiating the effectiveness of glyphosate salts such as the amine, ammonium, sodium, alkylsulfonium, alkylphosphonium, sulfonylamine, and aminoguanidine salts thereof by means of an environmentally friendly aqueous formulation made from a small number of ingredients, wherein the amounts of each of the components, including the glyphosate, can be kept very small, and wherein the resulting composition provides clearly observable herbicidal action, especially against broadleaf vegetation, in a short period of time after application. It would be particularly desirable if this need could be fulfilled by use of readily available, cost-effective materials while at the same time avoiding the inclusion of polyvalent metal-containing and metalloid-containing components in the formulation.
This invention is deemed to fulfill the foregoing need in an effective and highly efficient manner.